Recently, gallium nitride (GaN) High Electron Mobility Transistor (HEMT) devices have caught a lot of attention regarding their high potential to replace silicon (Si) or silicon carbide (SiC) for use as High Voltage (HV) devices. GaN HEMTs are typically fabricated by applying ohmic source and drain contacts and a Schottky gate contact on top of an epitaxially grown structure including an aluminum gallium nitride (AlGaN) barrier layer on a GaN channel layer.